The present invention generally relates to the field of capacitors, and more particularly related to a non-polarized capacitor and to a non-polarized tantalum capacitor array.
The present subject matter generally concerns a non-polarized tantalum capacitor and corresponding capacitor array. More particularly, the disclosed technology enables a non-polarized tantalum capacitor array with improved volumetric efficiency and reduced footprint.
Tantalum capacitors are known for their high capacitance value and compactness. Non-polarized tantalum capacitors are traditionally provided by connecting two polarized tantalum capacitors together, and more particularly are most often provided by electrically and mechanically connecting the cathodes of two polar tantalum capacitors together and by having the anodes provide the terminal access to the capacitor. Despite the existing compactness of known polar and non-polar tantalum capacitors, and tantalum capacitor arrays, there are constant efforts to reduce the volume, and more particularly, the footprint of these electronic components. This in turn allows the miniaturization of the devices in which these components are used.
An additional known challenge with tantalum capacitors is the fragility of the anode rod, particularly where it protrudes from one end of the capacitor. Mechanical and electrical connections, e.g. of leads or circuit boards, to the anodes often results in breakage, and thus shorting or a lost connection to the remainder of the capacitor. This problem is compounded by the fact that connections to the tantalum anode rods are also susceptible to failure. These connections are typically made with leads of a solderable material, such as nickel or tinned nickel, which is difficult to weld to the tantalum and results in a very fragile connection.
In order to protect the anode rods, and the connections to the anode rods, it is typical to encase the rods and connections, and the entire capacitor assembly in a substantial quantity of potting material. This substantially increases the volume of polar, and even more so, of non-polar tantalum capacitors. In addition to increased volume, the material and manufacturing costs are thus increased, and the footprint of the resulting capacitor or capacitor assembly is also increased.
As an example, U.S. Pat. No. 4,984,134 discloses a non-polar tantalum capacitor that is produced by laying two polar capacitors end-to-end, with the tantalum rods touching. After the tantalum rods are welded together, the area between the polar capacitors and extending down the sides of the capacitors is encased in potting material.
However, significant improvements over this design are still possible and desirable, particularly regarding footprint size, which is a critical factor in the efficient use of available circuit board surface area. In addition, although the design uses less potting material than in traditional designs, still a significant amount is used, resulting in higher manufacturing and part costs. Finally, while the reliability of the anode weld may be improved over traditional methods, it is at the cost of precious circuit board area and overall volume.
The disclosures of foregoing United States patents are hereby fully incorporated into this application by reference thereto.
The present subject matter recognizes and addresses various of the foregoing drawbacks and other shortcomings encountered in the prior art of tantalum capacitor technology. Thus, broadly speaking, a principal object of the presently disclosed technology is to provide an improved tantalum capacitor. More particularly, the disclosed non-polarized tantalum capacitor can be formed as a single capacitor unit or as a capacitor array.
It is another principal object of the present subject matter to provide compact non-polar capacitors, and compact non-polar capacitor arrays, with reduced volume, and significantly reduced footprint.
Yet another object of the present technology is to provide capacitors and capacitor arrays that are relatively simple and inexpensive to produce.
A still further object of the present subject matter is to provide simple and secure features for electrical and mechanical connection between the polar capacitors that are combined to form the non-polar capacitors. Further, the connection between the capacitor or capacitor array and the destination substrate is made in a simple and reliable fashion.
Additional objects and advantages of the present subject matter are set forth in, or will be apparent to those of ordinary skill in the art from, the detailed description herein. Also, it should be further appreciated by those of ordinary skill in the art that modifications and variations to the specifically illustrated, referenced, and discussed features and steps hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitution of equivalent means and features, materials, or steps for those shown, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.
Still further, it is to be understood that different embodiments, especially different presently preferred embodiments, of this invention may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features or steps or configurations thereof not expressly shown in the figures or stated in the detailed description).
Some embodiments of the present subject matter provide non-polar tantalum capacitors of reduced volume and with a reduced footprint. Other embodiments may provide non-polar tantalum capacitor arrays of reduced volume and with a reduced footprint.
In some embodiments of the present technology, each pair of polar tantalum capacitors is provided with, among other things, a conductive material for attachment to the anode rods protruding from each of the tantalum capacitors. This conductive attachment provides the electrical and mechanical connection that produces a non-polar capacitor from two polar capacitors, each of which has a capped main body to otherwise insulate them from each other.
In other embodiments of the present subject matter, the anode rods protruding from the polar tantalum capacitors are bent towards each other, then welded. The space between the polar capacitors, and the welded anode rods, are then filled with an insulating material, which also holds the non-polar capacitor together.
Additional embodiments of the subject tantalum capacitor technology provide capacitor arrays produced by attaching multiple non-polar capacitors together. These arrays may be attached with conductive connectors, such as printed circuit boards (PCBs), that provide the electrical connection between each pair of polar capacitors, and the mechanical connection between all the polar capacitors of the array. Other arrays are held together with an encapsulating insulating material that is provided over the welded anodes of each pair of polar capacitors, and between the capacitor bodies.
A still further embodiment of the invention provides an insulating shell into which the polar capacitors are placed. The anode rods are bent and welded, and an encapsulant protects and insulates the anode rods.
Additional embodiments of the present subject matter, not necessarily expressed in this summarized section, may include and incorporate various combinations of aspects of features or parts referenced in the summarized objectives above, and/or features or parts as otherwise discussed in this application.
Thus, the present invention provides a non-polar tantalum capacitor and a non-polar tantalum capacitor array that, inter alia, have a reduced volume and a reduced footprint. Reduced volume and footprint allow devices containing the capacitor or capacitor array of the present invention to be smaller, or allow additional components to be introduced into the device. These advantages are critical in the present environment of miniaturization.
Other advantages of the present invention include (but are not limited to) reduced material costs, simplified manufacturing processes, and thus reduced manufacturing time and labor costs. The capacitor and capacitor array of the present invention may be used advantageously wherever an electrical package requires a relatively large capacitance value in a relatively small package, such as in an implantable medical device or other application.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the remainder of the specification.